As the need to reduce current in transceivers, radio frequency amplifiers, and other integrated circuits increases, the need to more accurately control currents of the integrated circuits also increases. In addition, an integrated circuit may require multiple current sources that have different temperature coefficients. As an example, a zero temperature coefficient (ZTC) current source may be used to develop a bias current. In some applications, a proportional to absolute temperature (PTAT) current source or an inversely proportional to absolute temperature (NTAT) current source may be useful to compensate for temperature drift. Furthermore, as power consumption requirements become more restrictive, there may be times in which a particular application needs to accurately set a bias current based upon an external reference element. For example, there may be a desire to set a bias current based upon one or more precision resistors coupled to the integrated circuit.
Even so, process drift and batch-to-batch differences may reduce the accuracy of internally generated currents and thereby reduce the yield of these integrated circuits. Thus, there is a need for a circuit and technique to generate process independent and batch independent current sources for integrated circuit applications to improve manufacturing yields.